diff --git a/lib/std/http/headers.zig b/lib/std/http/headers.zig
index a7a1464f99..cb232a3e3e 100644
--- a/lib/std/http/headers.zig
+++ b/lib/std/http/headers.zig
@@ -349,16 +349,14 @@ pub const Headers = struct {
     pub fn format(
         self: Self,
         comptime fmt: []const u8,
-        options: std.fmt.FormatOptions,
-        context: var,
-        comptime Errors: type,
-        output: fn (@TypeOf(context), []const u8) Errors!void,
-    ) Errors!void {
+        options: std.fmtstream.FormatOptions,
+        out_stream: var,
+    ) !void {
         for (self.toSlice()) |entry| {
-            try output(context, entry.name);
-            try output(context, ": ");
-            try output(context, entry.value);
-            try output(context, "\n");
+            try out_stream.writeAll(entry.name);
+            try out_stream.writeAll(": ");
+            try out_stream.writeAll(entry.value);
+            try out_stream.writeAll("\n");
         }
     }
 };
@@ -593,5 +591,5 @@ test "Headers.format" {
         \\foo: bar
         \\cookie: somevalue
         \\
-    , try std.fmt.bufPrint(buf[0..], "{}", .{h}));
+    , try std.fmtstream.bufPrint(buf[0..], "{}", .{h}));
 }
diff --git a/lib/std/io/out_stream.zig b/lib/std/io/out_stream.zig
index 03901f6672..876a3b4701 100644
--- a/lib/std/io/out_stream.zig
+++ b/lib/std/io/out_stream.zig
@@ -25,7 +25,7 @@ pub fn OutStream(
         }
 
         pub fn print(self: Self, comptime format: []const u8, args: var) Error!void {
-            return std.fmt.format(self, Error, writeAll, format, args);
+            return std.fmtstream.format(self, format, args);
         }
 
         pub fn writeByte(self: Self, byte: u8) Error!void {
diff --git a/lib/std/math/big/int.zig b/lib/std/math/big/int.zig
index 8fda3f647a..cef2bae98c 100644
--- a/lib/std/math/big/int.zig
+++ b/lib/std/math/big/int.zig
@@ -518,17 +518,15 @@ pub const Int = struct {
     pub fn format(
         self: Int,
         comptime fmt: []const u8,
-        options: std.fmt.FormatOptions,
-        context: var,
-        comptime FmtError: type,
-        output: fn (@TypeOf(context), []const u8) FmtError!void,
+        options: std.fmtstream.FormatOptions,
+        out_stream: var,
     ) FmtError!void {
         self.assertWritable();
         // TODO look at fmt and support other bases
         // TODO support read-only fixed integers
         const str = self.toString(self.allocator.?, 10) catch @panic("TODO make this non allocating");
         defer self.allocator.?.free(str);
-        return output(context, str);
+        return out_stream.print(str);
     }
 
     /// Returns -1, 0, 1 if |a| < |b|, |a| == |b| or |a| > |b| respectively.
diff --git a/lib/std/net.zig b/lib/std/net.zig
index de10a17640..9395d34f48 100644
--- a/lib/std/net.zig
+++ b/lib/std/net.zig
@@ -268,16 +268,14 @@ pub const Address = extern union {
     pub fn format(
         self: Address,
         comptime fmt: []const u8,
-        options: std.fmt.FormatOptions,
-        context: var,
-        comptime Errors: type,
-        comptime output: fn (@TypeOf(context), []const u8) Errors!void,
+        options: std.fmtstream.FormatOptions,
+        out_stream: var,
     ) !void {
         switch (self.any.family) {
             os.AF_INET => {
                 const port = mem.bigToNative(u16, self.in.port);
                 const bytes = @ptrCast(*const [4]u8, &self.in.addr);
-                try std.fmt.format(context, Errors, output, "{}.{}.{}.{}:{}", .{
+                try std.fmtstream.format(out_stream, "{}.{}.{}.{}:{}", .{
                     bytes[0],
                     bytes[1],
                     bytes[2],
@@ -288,7 +286,7 @@ pub const Address = extern union {
             os.AF_INET6 => {
                 const port = mem.bigToNative(u16, self.in6.port);
                 if (mem.eql(u8, self.in6.addr[0..12], &[_]u8{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff })) {
-                    try std.fmt.format(context, Errors, output, "[::ffff:{}.{}.{}.{}]:{}", .{
+                    try std.fmtstream.format(out_stream, "[::ffff:{}.{}.{}.{}]:{}", .{
                         self.in6.addr[12],
                         self.in6.addr[13],
                         self.in6.addr[14],
@@ -308,30 +306,30 @@ pub const Address = extern union {
                         break :blk buf;
                     },
                 };
-                try output(context, "[");
+                try out_stream.writeAll("[");
                 var i: usize = 0;
                 var abbrv = false;
                 while (i < native_endian_parts.len) : (i += 1) {
                     if (native_endian_parts[i] == 0) {
                         if (!abbrv) {
-                            try output(context, if (i == 0) "::" else ":");
+                            try out_stream.writeAll(if (i == 0) "::" else ":");
                             abbrv = true;
                         }
                         continue;
                     }
-                    try std.fmt.format(context, Errors, output, "{x}", .{native_endian_parts[i]});
+                    try std.fmtstream.format(out_stream, "{x}", .{native_endian_parts[i]});
                     if (i != native_endian_parts.len - 1) {
-                        try output(context, ":");
+                        try out_stream.writeAll(":");
                     }
                 }
-                try std.fmt.format(context, Errors, output, "]:{}", .{port});
+                try std.fmtstream.format(out_stream, "]:{}", .{port});
             },
             os.AF_UNIX => {
                 if (!has_unix_sockets) {
                     unreachable;
                 }
 
-                try std.fmt.format(context, Errors, output, "{}", .{&self.un.path});
+                try std.fmtstream.format(out_stream, "{}", .{&self.un.path});
             },
             else => unreachable,
         }
diff --git a/lib/std/net/test.zig b/lib/std/net/test.zig
index 087f965c4e..0dc3b3020d 100644
--- a/lib/std/net/test.zig
+++ b/lib/std/net/test.zig
@@ -29,7 +29,7 @@ test "parse and render IPv6 addresses" {
     };
     for (ips) |ip, i| {
         var addr = net.Address.parseIp6(ip, 0) catch unreachable;
-        var newIp = std.fmt.bufPrint(buffer[0..], "{}", .{addr}) catch unreachable;
+        var newIp = std.fmtstream.bufPrint(buffer[0..], "{}", .{addr}) catch unreachable;
         std.testing.expect(std.mem.eql(u8, printed[i], newIp[1 .. newIp.len - 3]));
     }
 
@@ -51,7 +51,7 @@ test "parse and render IPv4 addresses" {
         "127.0.0.1",
     }) |ip| {
         var addr = net.Address.parseIp4(ip, 0) catch unreachable;
-        var newIp = std.fmt.bufPrint(buffer[0..], "{}", .{addr}) catch unreachable;
+        var newIp = std.fmtstream.bufPrint(buffer[0..], "{}", .{addr}) catch unreachable;
         std.testing.expect(std.mem.eql(u8, ip, newIp[0 .. newIp.len - 2]));
     }
 
diff --git a/lib/std/os/uefi.zig b/lib/std/os/uefi.zig
index 81d13ac1c3..5d9a678ce8 100644
--- a/lib/std/os/uefi.zig
+++ b/lib/std/os/uefi.zig
@@ -5,8 +5,6 @@ pub const protocols = @import("uefi/protocols.zig");
 pub const status = @import("uefi/status.zig");
 pub const tables = @import("uefi/tables.zig");
 
-const fmt = @import("std").fmt;
-
 /// The EFI image's handle that is passed to its entry point.
 pub var handle: Handle = undefined;
 
@@ -29,13 +27,11 @@ pub const Guid = extern struct {
     pub fn format(
         self: @This(),
         comptime f: []const u8,
-        options: fmt.FormatOptions,
-        context: var,
-        comptime Errors: type,
-        output: fn (@TypeOf(context), []const u8) Errors!void,
+        options: std.fmtstream.FormatOptions,
+        out_stream: var,
     ) Errors!void {
         if (f.len == 0) {
-            return fmt.format(context, Errors, output, "{x:0>8}-{x:0>4}-{x:0>4}-{x:0>2}{x:0>2}-{x:0>12}", .{
+            return std.fmtstream.format(out_stream, "{x:0>8}-{x:0>4}-{x:0>4}-{x:0>2}{x:0>2}-{x:0>12}", .{
                 self.time_low,
                 self.time_mid,
                 self.time_high_and_version,